Reliability of Copper-Plated Through-Package-Via (TPV) in Glass Packages with in-Situ Stress Measurements Using Raman Spectroscopy

This paper reports direct in-situ stress measurements with microscale spatial resolution in glass using Raman spectroscopy. This new technique is used to assess the reliability of copper-plated laser-drilled through package vias (TPV) in ultra-thin bare glass interposers. Bare glass panels of 3"x3" size, with 137µm and 237µm thicknesses were fabricated with laser-drilled through-package vias at 30 µm and 60µm diameter respectively. Glass panels were sputtered with a thin layer of titanium and copper. These thin films on glass were oxidized in order to obtain a CuO layer that acts as the stress-sensing film. Test coupons were subjected to known mechanical stress by bending. Analytical calculations and finite element models were used to investigate the relation of stress in glass with the peak shifts in Raman spectra in order to obtain the piezo spectroscopic coefficients. The stress near TPVs was estimated based on the obtained piezo spectroscopic coefficients.